Lattice-dynamics effects on small-polaron properties

Abstract

This study details the conditions under which strong-coupling perturbation theory can be applied to the molecular crystal model, a fundamental theoretical tool for analysis of the polaron properties. I show that lattice dimensionality and intermolecular forces play a key role in imposing constraints on the applicability of the perturbative approach. The polaron effective mass has been computed in different regimes ranging from the fully antiadiabatic to the fully adiabatic. The polaron masses become essentially dimension independent for sufficiently strong intermolecular coupling strengths and converge to much lower values than those traditionally obtained in small-polaron theory. I find evidence for a self-trapping transition in a moderately adiabatic regime at an electron-phonon coupling value of Ӎ3. Our results point to a substantial independence of the self-trapping event on dimensionality.

Dynamic process of self-trapped polaron in photoexcited SrTiO3

“…6. Thus, our numerical works show that the formation of self-trapped polaron is insensitive to dimensionality, which is in accordance with the perturbative result [24]. …”

Bose–Einstein condensation of strongly correlated electrons and phonons in cuprate superconductors

“…Generally it leads to a lighter polaron compared with the nondispersive approximation. For example, comprehensive studies of the molecular Holstein model, in which the dispersive features of the phonon spectrum are taken into account, found much lower values of the polaron mass compared with the non-dispersive model [27].…”

Spectral properties of the Su–Schrieffer–Heeger model

“…As a remarkable feature of the polaron physics [11][12][13][14], the strength of the coupling drives the transition from a large size polaron (at weak couplings) to a small size polaron (at strong couplings). This transition [15] is accompanied by a sizeable enhancement of the effective mass whose value may change considerably according to the degree of adiabaticity and the peculiarities of the lattice structure [16,17]. In some systems however [18][19][20] the e-ph interaction modifies the electron hopping matrix elements thus leading to a momentum dependent coupling function.…”